1. Field of the Invention
The present invention relates to a structure utilized to contain a plasma and/or electromagnetic field within a desired space while maintaining high conductance across the structure and permitting gas flow through the structure.
2. Description of Related Art
Plasma processing is often used under circumstances where it is beneficial to restrict the presence of the plasma to a certain region in the chamber while maintaining the ability to flow gasses through the plasma containing region. Several methods of plasma containment are currently in practice, including magnetic confinement, inertial confinement and confinement by solid or nearly barriers. Inertial confinement works only for short periods of time and has been shown useful only in power generating and explosive devices. Magnetic confinement has strong limitations in its application to many industrial applications. Because of the shortcomings of inertial and magnetic confinement systems, industrial plasma confinement is most often achieved by using a physical barrier within the chamber to confine the plasma.
For systems confining the plasma by physical barriers, this has been accomplished by placing openings in the physical barrier for the gases to flow through. Plasma confinement has been maintained by making at least one dimension of the cross section of these openings similar in size or smaller than the plasma sheath or dark space as disclosed in U.S. Pat. Nos. 4,384,938 and 5,605,637. However, utilizing such small holes in the physical barrier has been found to lead to low conductance, particularly when the molecular mean free path is similar to or longer than the dark space. Further, these small holes tend to clog in the presence of a depositing chemistry such as is typically used in selective etching. This clogging not only restricts the useful lifetime of the chamber but creates continually changing process conditions which can reduce process yields.
In the case of highly selective etch chambers utilized in the semiconductor manufacturing industry, it is common to have plasma conditions where the molecular mean free path is long compared to the dark space of the RIE chamber and where there is the problem of film deposit on the physical barrier. Accordingly, there is a long-felt need for plasma barriers in RIE systems that have a high, relatively stable conductance and excellent plasma confinement properties even when the molecular mean free path is long compared to the dark space and/or when a film is being deposited on the barrier.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a barrier useful in systems that has a high, relatively stable conductance.
It is another object of the present invention to provide a barrier useful in systems that has excellent plasma confinement properties even when the molecular mean free path is long compared to the dark space.
A further object of the invention is to provide a barrier useful in systems that has excellent plasma confinement properties even when a film is being deposited on the barrier.
It is yet another object of the present invention to provide a system that incorporates a barrier having the aforementioned advantages.